Synthesis of 3-aryl-1 methyl-1-methoxy ureas



3,213,121" 1 SYNTHESIS on ennu ALgETHYLl-ME'IHOXY Donald L. Smatliers, Wilmington, DeL, assignor to E. I.

' 'du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware v I rawing. Filed June 22, 1959, SenNo. 821,641, 7 2' Claims. "(CL 260453) n This invention relates to the preparation of l-methoxy- 3,213,121 Patented Oct. 19, 1965 do not react with the hydroxylamine. It will ordinarily the desirable to add water if this was not used as a solvent 1-methyl-3-aryl ureas and is more particularly directed to processes which can be conducted in a single vessel" starting with anaryl isocyanate and a hydroxylaminc of Formula 2 and followed by a methylation.

It is most surprising that methylation of a compound of the following structure can beefiected selectively on the aliphatic nitrogen or on the oxygen attached thereto:

H 1) i n Xm R! where R R H, CH and at least one of R and R =H According to the present invention-it has been ascertained thatby methylation as hereinafter described the hydrogen groups represented in the above by R and R,

' can be replaced by methyl groups.

From the knowledge of the prior art, one would expect that the aryl nitrogen would be methylated preferentially to-the aliphatic nitrogen, particularly because it is more f acidic. Such acidic nitrogens are well understood to have a greater afiinity for the 1 reaction.

methyl group in a methylation Therefore, it might be expected that if the compound above were treated with a methylating agent one would where or carrier in the first step. The methylation proceeds as follows:

' l-methoxy-I-methyl-Maryl urea X=H, Cl m=l, 2, 3 Y=H, CH, n=1, 2 I R R,=H, CH, and at least one of R and R,=

. According to the present invention the sequence of reactions is conducted in such a manner that the aryl ureas can readily be converted to the 1-methoxy-l-methyl-3 aryl ureas to be produced according to the invention using the same equipment and without an intermediate separation of products.

The methylation is preferably conducted in water, the

product of Formula 1 being present as adispersion and thus slurried in water. A solvent such as above described can also be present. The compound of Formula 1 can be entirely dissolved in the water-solvent system or can be present only as a slurry in which the compound is. but

obtain a methyl group only on the aromatic nitrogen or might obtain no methylation at all. If neither of these occurred, one might expect rearrangement of the structure under conditions severe enough to effect methylation.

Surprisingly it has been found that if the compound above listed is methylated as herein described, the hydrogen on the aliphatic nitrogen can easily be replaced in good yield and without affecting the hydrogen group on the aromatic nitrogen.

The reaction of an aryl iso'cyanate with a hydroxyl amine proceeds as follows: 1

aryl urea The product of reaction thus obtained together with the solvent or solvents in which it is conducted can without intermediate separation of product be used in the methyla tion step. The solvents which can be used include such common reaction media as dioxane, alcohol, cyclohexanol, isopropanol, and other such reaction media which little dissolved.

The temperatures of the methylation should be enough above freezing so that the system will not be solid. Otherwise it cannot be handled. practical can be used. Higher temperatures can be employed and where Rgis hydrogen the temperature should not greatly exceed 20 C. Where R, is methyl the temperature may go as high as the reflux temperature of the particular system, whether water alone or water with another solvent. It is preferable, ordinarily, to uselemperatunes not greatly in excess of C. 1 Because of the high expense of cooling and the relative stabilities of the starting amines, it is easily seen that ordinarily it will be preferred to use O-methylhydroxylamine as the starting 1 amme.

Any methylating agent such as one fromthe groupmethyl halides such as methyl chloride, methyl bromide, is added to the compound 1 in water or other liquid, as described, together with a suitable base. The amount of methylating agent can be that customarily used, say 2 to 4 molecular equivalents The amount of base and rate of addition is so adjusted that the pH remains between 7 and 11. As shown one may use sodium hydroxide, potassium hydroxide, sodium or potassium carbonate, and other such commonly employed bases.

The methylation should of course be conducted with good stirring so that local concentrations of the "methylsting agent are avoided as otherwise the use of the methylating agent will be excessive.

The present process has the advantage that it uses readily available raw materials of comparatively low cost for the production of 1-methoxy-1-methyl-3-aryl ureas. Ordinarily one might attempt to produce such an aryl urea by reaction of an aryl isocyanate with an appropriate amine. The amine to produce the products desired Temperatures aslow as are l and methyl iodide,

ared. ,7

The processes above generally. described can be illusrated with a typical aryllisocyanate and withihree dif erentaminesr I Y b YARYL ISOCYANATE PLUS HYDROXYLAMINE -To a well-stirred 2 to 20%,Qpreferably, to

i'que'o us solution of hydroxylamine, maintained at temieratures between --'l0-' C. and "v. C., preferably 10? C, to.0 C.-, is added between 0.25 andal; prefer lb1y 0 .81, molecular'equivalents of SA-dichIOrophenyL; socy'anate, optionally dissolved. inja water-miscible; inert olvent such as dioxane. The rateof addition will vary} vith'the size of the run and the elfectiveness of the cool-- 1 ng bath (highly exothermic'reaction) but generally will 'equire between 5 and 120 minutes, preferably .lO-ZOI minutes. The resulting-reaction mixture can be used di-"T rectly although'it becomes niore tractable water is I dded and dis allowed to stir for '10'-45 minutes before; aroceeding;

= Th,e reaction-as-just"describedbroceeds asiollowsi i Theyreaction niixtureobtained asab'ove is used in he following'methylation. Between=2 and 4, referably 2.5 Qto 3, molecular equivalents based ,on hydroxylanrine,

3f an alkali or alkaline earth base, such as sodium hyiroxide, dissolved in water, is added attemperatures be :ween 5"' and 20 'C;-, preferablyfbet'ween 5C. and

n the range between 5. C. and 0., preferably 10" 3'. tollS? C .Whenaddition" is complete,'.the reaction q nixturefis allowedv to ;warrn"spontaneously" butis ree itr'ained from exceeding 351 0. '40'isi1b '1 a Y v Atwt'J-r'socmmrag itan'tiallvpure product isrecovered-by filtration. 1'

The r actionvjust described-proceedsasvfollowsz;

4 I u i NOE-1:101 NH OwNHOHHiCHaMBM.

j' Instead of proceeding the ni'ethylation as above,

taneously withaqueous base so that the mix ure is in the range of pH 11, preferably 8-9;"a'nd'the temper-- ature lies-between? C; and 20 C.,-prefera bly 5 to 1'0? 0. When addition bf thedimethylsulfate is corn plete, the reaction mixture is allowed to warm spontaneously, but is restrained ,from exceeding a temperaiure of Cato C.,yadding'aqueous base 'as ne'eded to m'aintain thepH in the above range. Theproduetf is'r'ecovered by filtration.

'ARYL ISOCYANATE PLUS N METHYLP, HYDROXYLAMINE x .The reduction of nitrom'ethane'to l. l-"methylh ydroxyl amine is described byBeckmann Ann;365-211 11909).

Nitrometh'ane'is reduced byjz'in'c in an aqueous ammoniuntxchlo'ridesolutiont The resulting solution; "of .N- 7 5 vperatures between-5W0. and -'C1, preferably 80 C I i methylliydroirylamine --isiiltered to remove zinc salts, I cooled to -10? told-209 ,01, preferably --10 to.0 (2.,

stirred 'well, and between 0.2 and -0.8,-preferably Q 4.O.5

molecular equivalents, based on nit-r'ome'thane, of -3,4-\ Y dichlorophenylisoeyanate isadded 'optionally dissolved in a a water-iniscible ,-inert solvent such asdioxane; The rate v I .of addition-will vary'with the'sizej of the run and the' 'etfefctiverlesjs of the cooling b'ath (highly exothermic reaction), but'will .generally require S' to' minutes, preferably 10 20.n1iriutes. 'Ther'esulting mixture ca'n ,be" {used directly in the methylation step, but we have found I that there-is nior'e'jeconornical consumptionjofgdin ethyl sufzite'if thesupernatent liquidiss iphonedolfand-1re- I -placed. with an approximately-equaljyolurnecof water;

" .Thereactio 'ust described proceeds as follows: r c1 aucioi mrxon i 'added to thereaction product obtainedas above ,at t emvperatures'between ----5 C. and +20? 0., preferably 0 C. h toSf C; i's follo'wed by the additionof'between'l 1 and 2,-' p'referably l-l-.2 rn'olecula'r equivalents of dimethyl sulfate' lwhen additionjscomplete, the mixture I is .v allow'ed to spontaneously; but is restrained. from.

' ei'weedinglH35" to 40? Q. Theyproduet isrecovered q ty-mtmriqt,

-, I j The reaction-isles (1) 1 l0 C; This is followed bythe addition of between 2;; I X and 4, preferably 2.5: to .3, molecular equivalentsofi die neth'yl sulfate at such a rate that the temperature 'st'aye I followsi a v l fl I B To a well-stirred 2%-25%, preferably 5%-.-1$ aque- .ous solution of O-methylhydroxylamine,1'at temperatures betweenw -ltl C; and +20'C., preferably- 5? C. 'to +5}C.',"is;added between 0.5 and 1,"1:vreferably 9-1,

molecular equivalents of 334-dichlorophenylisocyanatg;op- .tionally dissolved in a'wate'r-miscible, inert qlvent such as dioxanee The rate of'addition'willvaryvwith the sizeoi the and thejeflectiveness of "cooling, biltlflill generally e -5to' 129 m nutes; preferably ltlzdmiuut'es; 'Tbere'action proce'eds-asjfollowsz Between lfand 2, preferably 1.24.5, r nolecular equivaaction productprepared'above. An aqueous solution of an'alka-li or alkaline earth base, preferably sodium hywdroxide, is added as needed to -maintain the solution in the range off-pl-fF-ll, preferably pH1-8-9. .Extema l heat Y is' applied'asineeded to keep the reaction mixture at tern- .a aimd Nom-i-cmsoH f.

PLUS 1 enema-vert x reference should be had to to 90 C. To insure complete conversion of the intermediate urea to the desired product, it is found to be generally helpful to'add an a'dditional0.5- 1.5, preferably. 1- 1.5, molecular equivalents-of dimethylsulfate afterabout f 10-30 minutes, maintaining the pH and temperature as j above. Allowing 1030 minutes for the reaction to be completed, the product is recovered by filtration after. cooling the reaction mixture to room temperature.

The reaction is as follows: (9)

i O OCH:

In order that the invention may be better understood the following illustrative examples Example 1.-1 -methxy-1-methyl-3-(3,4-dichl0r0phenyl) urea starting with hydroxylamine To a well-stirred solution of 66 parts of hydroxylamine in 500 parts of water (prepared by neutralization of aqueous hydroxylamine hydrochloride with aqueousbase) at temperatures between 2 C. and 5 -C. is slowly added a solution of 188 parts of 3,4-dichlorophenylisocyanate in 200 parts of dioxane. Stirring is continued for 30 minutes after addition is complete and then interrupted. The solids' are allowed to settle and the supernatent liquid is siphoned minutes, without cooling, the mixture is filtered,.and

the product dried.

urea, starting with O-rirethylhydroxylamine To awell-stirred solution of 47 parts of O-methylhyi droxylamine in 350 parts of water (prepared from aquecontinued but cooling is discontinued and 150 parts of dioff. 7 (The solids are stirred with 1000 parts of water,

. which is then siphoned off as above.) A solution of 110 parts of sodium hydroxide in'1000 parts of waterisadded to the solid residue and the slurry is refrigerated-to 0-5 C. Stirring is started, arid 315 parts of dimethylsulfate is added gradually so that the temperature remains in the range of 0 C. to 5 C. To effect complete interaction, the reaction is allowed to warm up to room temperature spontaneously with continued stirring. The resulting mixture is filtered and theproduct dried, yielding 198 parts of essentially pure material.

Example 2.-1-meth0lty-I-methyl-3-(3,4-dichlorophenyl) urea, starting with hydroxylamine -To a well-stirred slurry of 1-hydroxy3-(3,4-dichloro phenyl)urea prepared as in Example 1, at temperatures between 5 C; and 10 C., 315 parts of dimethylsulfate is added gradually and concurrently with a solution of'40% sodium hydroxide so as to maintain the mixture in the range of pH-8-10. To effectamore complete interaction, stirring is continued until the combined mixture warms up spontaneously to 25 C. .The product is recovered'byr filtration and dried.

Example 3.1 methoxy-I-mthyl-3- (3,4-dichl0r0phenyl urea, starting with N-methylhydroxylamine To a solution of 122 parts ofnitromethane and 74. parts of ammonium chloride-in 100 parts of water, stirred at 0 C.-15 C., is added a total of 300 partsof zincdust over a three-hour period. The resulting mixture is filtered. The filtrate containing N-methyl-hydroxylamine is stirred,

maintained at a temperature range of -5 C. to -2 C.,

while a solution of 188 parts of 3,4-dichlorophenylisoous O -methyhydroxylamine hydrochloride and aqueous hase) at 0 C. to 15" C., is added gradually a solution of g 188 parts of '3,4-dichlorophenylisocyanate dissolved in 200 parts of dioxane. When addition is complete, stirring is 'methylsulfate is added all at once. A 40% solution of sodium hydroxide is added as needed to maintain the-mixture in the range of pH 8-9. Simultaneously, the mixture is 'heated and the temperature maintained in the range of C. to C. After 15 minutes of continued stirring at 80 C. 90 C. the reaction is again treated with parts of dimethylsulfate and suflicient alkali to maintain the pH range of 8-9. The stirring mixture is cooled gradually to 20 C. to 25 C. andfiltered. The yield of essentially pure l-methoxy-l-methyl 3-(3,4-dichlorophenyl)urea is nearly quantitative.

Examples 5 through 12 Following the procedure of Examples 1 through 4 other l-methoxy-1-rnethyl-3-arylureas can efiicaciously be prepared. The hydroxylamine and arylisocyanate employed and the products obtained are listed in Table I. The amounts of starting materials are equivalent on a molecular basis to those of Examples 1 through 4.

TABLE 1 Hydroxylamlne Arylisocyanate Product l-methoxy-lmethyl-3-(4- ehlorophenyburea.

l-methoxy-lmethyl-3- 2,4,5- trlehlorop enyl) urea Hydroxylamine.-. 4-chlorophenylisocyanate.

2,4,5-trlchlorophenylisoeyanate.

l-methoxy-lmethyH-(Q- methyH-ehlorophenyl)urea.

l-methoxy-lmethy1-3-(3- chlorophenyDurea.

l-methoxy-lmethyl-3(4- methylphenyl) urea. l-methoxy-lmethyl-342- methylphenyl) urea. l-methoxy-lmethyl-342,4- dlmethylphenyl) urea. l-methoxy-lmethyl-3-(4-chloroethyl- 2,5-dim phenyl)urea.

z-methyH-chlorophenylisocyanate.

B-ehlorophenyllsocyanate.

t-methylphenylisocyanate.

N-methylhydroxylamine.

Z-methylphenylisocyanate.

2,4-dimethylpheny1- Oqneth lh y y lsocyanste.

droxylamine.

4 ehloro-2,5-dl-,

methylphenyltsocyanate.

Iclaim: a 1. The process for preparing a compound of the for- H Xu El Y- C H mula:

wherein X is selected fromthe group consisting of hydrogen and chlorine; m is a positiveinteger less than 4;

selected 1 from the group consisting 'methyl; and n is a positive integer less than 3;

of hydrogen and which comprises reacting acdmpound of the formula: v References Cited by the Examiner 7 I x H 0 I H i I UNITED STATES PATENTS 2 I n 2,663,729 12/53 Searleet a1. -2 260-553 H? y 2,673,878" 3/54 Cusic'; 260--553 7 i 'Yn 2,775,617 12/56 Shapiro' j 260-567.6 in an alkaline medium with a compound selected from 2,382,292 4/59 C 'tg et al. 260--567.6 the group consisting of dimet-hyl sulfate, methyl chloride, I 2,902,356 V 9/59 Luckenbaugh 260-553 methyl bromide and'methyliodide'. v I OTHER REFERENCES 2. The-process for prepa rmg a compoundof-the for Fieser Organic Chemistry (third 6d pp 136 v v T i' I y Y 228, 229. I 1 Hurd, J. Amer. Chem. Soc., vol. 45 (1925), pages 1--NH-GN -OGH, 1 1472. 89 (pages 1473 and 1481 are particularly relied Ha on). i

I Saunders Co., Philadelphia, p. 136 (1951).

O Y c1 NH-l :-EII-or v NICHOLAS s. RIZZO; Primary Examiner.

o IRVING MARCUS, DUVAL T. MCCUTCHEN, WALTER A. MODANCE, Examiners.

which comprises reacting a compound of the formula with dimethyl sulfate in an alkaline medium.

Noller, Chemistry of Organic Compounds, 15!: ed., 

1. THE PROCESS FOR PREPARING A COMPOUND OF THE FORMULA: 